Currently, material drying can be classified into spray drying and freeze drying. The conventional spray drying cannot dry thermosensitive materials, thus, its application fields are limited. Freeze drying has disadvantages of a long drying time and a high cost.
In view of the technical deficiencies in the above material drying manners, spray freeze drying is researched and developed. The spray freeze drying is a new particle preparation technology in recent years which combines spray drying with freeze drying, and has been successfully applied in protein aspect as well as inhalable medicine and high value-added food industries.
The process of spray freeze drying includes three stages, i.e., atomizing, freezing and drying. Specifically, in the process of drying, firstly the material is atomized into fine liquid droplets by an atomizer, and then contacts with a refrigeration medium to be frozen, and finally, is performed with vacuum freeze drying or fluidized bed drying.
However, in the process of the conventional spray freeze drying, bumping phenomenon may occur when liquid droplets contact with a refrigeration medium. In addition, disadvantages such as waste caused by volatilization of the refrigeration medium with a low boiling point and uncontrollable temperature of the refrigeration medium are also presented, which has an adverse effect on the shape, appearance and performance of the particles and the development of resource saving strategy in China.
Therefore, it is necessary to put forward a further technical solution aimed at the above issues.